KZ 750 H3 - Valves and Compression

Can anyone tell me... Using a valve spring compressor, can I replace the valve seals without taking the head off? I just read a little blurb that said it is possible, but not sure about this motor... It would seem you would remove the lock washer, and spring, but then the valve would drop down in the motor, would it not?

Okay!

First try, I got all the celarances in spec, except one which is a *little* wide. I'm probably not going to bother fixing it.

I noticed the cam chain sort of lifts off the rear sprocket teeth slightly at one point, actually right around TDC for 1 and 4... Everything is in spec, tight chain front and back, but the slack seems to change in between the sprockets as the cams turn. I can't imagine that is normal...

Do I have a problem with the tensioner or the cam chain itself?

For what it is worth, I decided to say "eff it" and button it up and check compression.

Now at 125 - 120 - 120 - 140!

It runs much better, but #4 still isn't firing, still popping out the carbs, and still has erratic idle. I realize I shouldn't have run it without being 100% sure on the camchain, but I spun it a bunch with no funny noises, and rechecked the timing marks a dozen times and everything seemed good...

Gettin' there.

WBPDX wrote:

Can anyone tell me... Using a valve spring compressor, can I replace the valve seals without taking the head off? I just read a little blurb that said it is possible, but not sure about this motor... It would seem you would remove the lock washer, and spring, but then the valve would drop down in the motor, would it not?

I do not think it is possible on a kawi head. You can keep pressure on the valve with compressed air into the spark plug hole, but I have never seen a tool that would be able to remove the springs from the top on a Kawi head. I also think it would be nearly impossible to get the seal off with the valve stem still in it.

WBPDX wrote:

Okay!

First try, I got all the celarances in spec, except one which is a *little* wide. I'm probably not going to bother fixing it.

I noticed the cam chain sort of lifts off the rear sprocket teeth slightly at one point, actually right around TDC for 1 and 4... Everything is in spec, tight chain front and back, but the slack seems to change in between the sprockets as the cams turn. I can't imagine that is normal...

Do I have a problem with the tensioner or the cam chain itself?.

My guess would be chain.


WBPDX wrote:

For what it is worth, I decided to say "eff it" and button it up and check compression.

Now at 125 - 120 - 120 - 140!

It runs much better, but #4 still isn't firing, still popping out the carbs, and still has erratic idle. I realize I shouldn't have run it without being 100% sure on the camchain, but I spun it a bunch with no funny noises, and rechecked the timing marks a dozen times and everything seemed good...

Gettin' there.

The compression is better, I'm not sure if it is in spec for a 750 four cylinder. It would be at the very bottom of service limit for a 750 twin.

That's dead-stone-cold though, RIGHT after the valve adjustment. Those numbers will likely increase significantly when warm.

If your valve lash is within .003"-.009" and your tensioner is tight those compression figures are normal for a motor with that many miles on it. The manual says 170-180 but I believe that to be way overkill for anything other than racing.
I think the biggest thing to look for is a big variation between the cylinders - that suggests issues. 10 psi between cylinders is no big deal as long as the throttle response is good.

My H1 manual says anything from 109-171 PSI is usable with less than a 14 PSI difference between any two cylinders.

WBPDX wrote:

That's dead-stone-cold though, RIGHT after the valve adjustment. Those numbers will likely increase significantly when warm.

True, probably will go up some.

WBPDX wrote:

Okay!

First try, I got all the celarances in spec, except one which is a *little* wide. I'm probably not going to bother fixing it.

I noticed the cam chain sort of lifts off the rear sprocket teeth slightly at one point, actually right around TDC for 1 and 4... Everything is in spec, tight chain front and back, but the slack seems to change in between the sprockets as the cams turn. I can't imagine that is normal...

Do I have a problem with the tensioner or the cam chain itself?

That's normal for the cam chain to do that when you have the cover removed, look inside the cam cover right above where the chain runs, you'll see the cam chain slipper that keeps the chain from doing that.

When you first removed the cam cover there should have been slack in the chain between the cams, if you don't lock out the cam chain tensioner it will proceed to take up that slack. Then when you install the cam cover there is no slack for it to push down on, so something has to give, as in break.

Do a search for gpz750 faq on Google, the FAQ has really good instructions and explanations for all this, and it applies to all the air cooled 750 fours.